Increase frame limit in bubble bar screen test

50x run ABTD (passed): https://android-build.corp.google.com/abtd/run/L87100030006646570

Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 366544536
Test: atest BubbleBarViewScreenshotTest and ABTD above

Change-Id: If6683001bf3e87a60500b99d022d956f76dd9da4